package Week2.J0424;

import java.util.Scanner;

public class 跳台阶_xv {
    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);
        int n = scanner.nextInt();
        if (n == 0 || n == 1) {
            System.out.println("1");
            return;
        }
        int a = 1;
        int b = 1;
        int c = 0;

        while (n-- > 1) {
            c = a + b;
            a = b;
            b = c;
        }
        System.out.println(c);
    }
}
